DE 101 39 139 A1 relates to a dosing system for dosing a reducing agent for exhaust gas aftertreatment. The reducing agent is, in particular, urea or an aqueous urea solution. This is used to reduce nitrogen oxides contained in the exhaust gas from an internal combustion engine. A delivery device for delivering the reducing agent from a storage container to an exhaust pipe carrying the exhaust gas is provided. The dosing apparatus furthermore comprises a metering device for the dosed feeding of reducing agent into the exhaust pipe, the delivery device comprising a pump and the metering device comprising a dosing valve with an outlet element. The metering device is set up for mounting close to or on the exhaust pipe, thus allowing the outlet element to project into the exhaust pipe, and the delivery device is set up in such a way that it is mounted on or in the storage container. The delivery device and the metering device form separate modules connected by a connecting line.
DE 10 2004 051 746 A1 relates to a reservoir module for a reducing agent and to a dosing system. According to this solution, a reservoir module housing is provided, and a dosing system for dosing a reducing agent into an exhaust system is arranged within a reservoir chamber of the reservoir module housing. According to this solution, the dosing system is designed as a compact built-in module.
DE 10 2006 027 481 A1 relates to a vehicle reservoir for a liquid reducing agent, especially a urea solution. The vehicle reservoir for accommodating an aqueous urea solution for reducing nitrogen oxides in the exhaust gas from internal combustion engines is manufactured from plastic. The vehicle reservoir advantageously has a functional unit which comprises at least one pump, at least one pressure control valve, at least one internal reservoir with an integrated electric heating system and at least one suction line. The functional unit is advantageously inserted into an opening in the reservoir and seals off the latter in the manner of a cap.
The reducing agent is transported from the reservoir to the dosing module in a conduit by a pump, which represents the delivery module. Pressure control is exercised on the actuator side by means of the speed of the pump motor and, in the feedback branch, by means of a pressure sensor. A permanent return flow restrictor in the vicinity of the pressure generator gives the hydraulic system a high pressure stability from the point of view of control. To exclude possible damage to the system in the event of freezing, the system is ventilated, when the engine is switched off, by reversing the polarity of the delivery pump and simultaneously opening the dosing module to the exhaust gas. In the event of freezing, the reducing agent expands by about 10% of its volume.
The reservoir holding the reducing agent contains an anti-surge pot, in the lower area of which an electric heating element is generally positioned. To be able to ensure readiness for dosing within an acceptable time and with a minimum heating power at low outside temperatures, heating is restricted to the area of the anti-surge pot. This is achieved by virtue of the fact that the plastic wall of the anti-surge pot as it were insulates the contents of the pot from the overall contents of the reservoir. The entire heating energy is thus available for thawing the volume of reducing agent held in the anti-surge pot.
In order to manage with a single fill of the reducing agent reservoir between two service intervals, the reducing agent reservoir generally holds between 20 and 30 liters of reducing agent. The driver thus has no contact with the reducing agent, the reservoir being refilled during the service. However, implementing a 30-liter reservoir for reducing agent within today's bodies is extremely difficult, given the ever smaller amount of installation space available. All reservoirs and the geometries thereof are highly project-specific and this entails a large variety as regards the shape of the reservoir, the shape and size of the anti-surge pot, the heating elements used and the level sensors. Moreover, the reservoirs require individually tailored thermal insulation and fastening means. This is associated with a very wide variety of different versions, and this in turn entails very high costs.
Owing to constantly increasing fuel prices and a pressing requirement for CO2 reduction, a reduction in fuel consumption will be indispensable in future. Since the removal of nitrogen oxides from the exhaust gas of internal combustion engines by means of an aqueous urea solution as a reducing agent allows optimum design of the internal combustion engine with regard to fuel consumption, the SCR (selective catalytic reduction) method will play a preeminent role. Owing to the saving in fuel consumption required for CO2 reduction, carrying 30 liters of reducing agent in the motor vehicle at all times is no longer acceptable. The result will be that there will be a drastic reduction in the size of the reservoir for the reducing agent and the reservoir will accommodate a volume of reducing agent of the order of between 2 liters and 10 liters and will have to be refilled by the driver at intervals of about 2000 to 5000 km, depending on operating conditions. Refilling by the driver will be accepted because, in particular, an external refilling facility for refilling the reducing agent reservoir is already being provided nowadays.